feat(status): show each served profile's shared-listener callback URLs

hermes -p <name> gateway status, hermes gateway status and hermes status (under
Serves:) list the /p/<profile>/<path> URL per inbound-port platform the live
multiplexer serves, read from the <profile>:<platform> ingress_url in the default
home's gateway_state.json (hermes_cli/gateway_multiplex_served.py). The dashboard's
messaging payload carries the same ingress_url and the Channels page renders it.
The dashboard's 409 guard now covers only api_server/webhook (the mirrored pair):
enabling Twilio/LINE/Teams/... on a secondary is allowed because the gateway serves
it.

web/src/lib/api.ts

@@ -1590,6 +1590,8 @@ export interface MessagingPlatform {
   error_message: string | null;
   updated_at: string | null;
   home_channel: { platform: string; chat_id: string; name: string; thread_id?: string } | null;
+  /** Multiplex secondary served on the default profile's shared listener: the vendor callback URL. */
+  ingress_url?: string | null;
   whatsapp_setup?: {
     mode?: string;
     allowed_users_set?: boolean;

web/src/pages/ChannelsPage.tsx

@@ -567,6 +567,12 @@ export default function ChannelsPage() {
                           {platform.error_message}
                         </span>
                       )}
+                      {platform.ingress_url && (
+                        <span className="text-xs text-muted-foreground break-all">
+                          Callback URL (shared listener):{" "}
+                          <code className="font-mono">{platform.ingress_url}</code>
+                        </span>
+                      )}
                     </div>
                   </div>